First principles modeling of soft X-ray spectroscopy of complex systems

Abstract: The electronic structures of complex systems have been studied by theoretical calculations of soft x-ray spectroscopies like x-ray photoelectron spectroscopy, near edge x-ray absorption fine structure, and x-ray emission spectroscopies. A new approach based on time dependent density functional theory has been developed for the calculation of shake-up satellites associated with photoelectron spectra. This method has been applied to the phthalocyanine molecule, describing in detail its electronic structure, and revealing the origin of controversial experimental features. It is illustrated in this thesis that the theoretical intepretation plays a fundamental role in the full understanding of experimental spectra of large and complex molecular systems. Soft x-ray spectroscopies and valence band photoelectron spectroscopies have proved to be powerful tools for isomer identification, in the study of newly synthesized fullerene molecules, the azafullerene C48N12 and the C50Cl10 molecule, as well as for the determination of the conformational changes in the polymeric chain of poly(ethylene oxide). The dynamics of the core excitation process, revealed by the vibrational fine structure of the absorption resonances, has been studied by means of density functional and transition state theory approaches.